Field of the Invention
The invention relates generally to electrical surge suppression systems, and more particularly to systems and methods for monitoring and providing remote notification of failures of surge suppression capabilities in drive systems for downhole equipment such as electric submersible pumps (ESPs).
Related Art
Oil and natural gas are often produced by drilling wells into oil reservoirs and then pumping the oil and gas out of the reservoirs through the wells. Often, the oil is pumped out of the wells using ESPs. Electrical power is provided from an electrical grid to electrical drive systems at the surface of the wells, and these drive systems provide electrical power at the appropriate voltages and frequencies to the ESPs to allow them to pump fluid from the wells. Variable speed drives (VSDs) are commonly used to drive ESPs. Because VSDs provide advantages such as improved energy usage, improved process control, increased production and increased reliability with respect to competing technologies, the use of these drives has increased substantially in recent years.
There may be a number of VSDs that are connected to the same power grid. Because a variable speed drive is a non-linear load, each VSD may draw current from the power grid in a non-linear fashion. There may also be other non-linear loads connected to the power grid. This non-linear loading of the power grid may cause the grid to experience distortion or disruptions as it provides power to the VSDs. In addition, power distortions may originate from other sources—either man-made or natural. The distortion or disruptions may result in electrical surges that can damage the VSDs or the equipment that is driven by the VSDs. Consequently, some VSDs incorporate integral surge suppressors that mitigate surges in the power provided by the electrical grid from propagating to or through the VSDs and damaging the VSDs or other equipment.
Normally, a surge suppressor is designed to prevent a single damaging surge of power. Typically, after a surge suppressor has experienced a power surge and prevented the surge from damaging the VSD, it is no longer capable of preventing further surges from damaging the VSD or other equipment. Often, upon inspection of a VSD, a field service technician, engineer or other operator of the well will find that the surge suppressor has “done its job” and is no longer working. Frequently, there is no external indication that the surge suppression capability has been compromised and the drive is consequently at higher risk than it was before failure of the surge suppressor. Failure of the surge suppressor may also provide a more general indication that there are power anomalies on that line or system. (“Failure” is used here to indicate that the surge suppressor is no longer capable of suppressing a power surge, rather than that the surge suppressor was defective or did not initially function to suppress a power surge.)
Since the operators of the well may not be aware of the surge suppressor failure until someone physically inspects the drive system, the drive may continue to operate without surge protection for a significant amount of time. During this time, there is an increased risk of damage to the drive and/or downhole equipment, and a resulting increased risk of costly interruptions of well operations for repairs. It would therefore be desirable to provide systems and methods for providing notifications to well operators or others upon failure of a surge suppressor in a drive system for downhole equipment in order to allow timely remedial actions, such as repair or replacement of the surge suppressor.